The present invention relates to a method and apparatus for applying a visible indication means to a surface, and more particularly relates to a method and apparatus for applying reflective elements as a line marking system used on road surfaces.
Line markings, for instance on a road infrastructure are important features for separating lanes of traffic and indicating to a driver safe overtaking zones in situations where adjacent lanes have opposing directions of travel of vehicles. It also provides a clear indication of the road edge and centre line of the road with day and night visibility and are an accepted safety requirement in most countries.
Line marking to a road surface is generally made by applying a paint to the road surface, however, problems arise where over a period of years the paint surface wears and becomes faded which requires further application of the paint. Such a process is expensive and where weather conditions, such as rain, make visibility poor and particularly at night time, this creates a potential hazard to drivers of vehicles where the lines are not clear.
Improvements have been made to increase visibility, particularly at night time, by the use of reflective elements such as glass beads in the surface of the line marking. Thus when light from a vehicle strikes the bead it is reflected back towards the driver of the vehicle enabling the driver to see the road markings and determine where the edge and centre lines lie. The process of placement of the beads within the line marking typically involves the beads falling onto an adhesive or paint stripe that has previously been applied to the road surface. When the adhesive or paint cures, the beads become fixed to the road surface. Such a process has limitations in terms of the reflectance, also known as retro-reflectivity, which limits the overall effectiveness of the road line marking. As the beads are applied to the previously painted line from a moving vehicle, they bounce and scatter having the disadvantages that the beads are either covered with the pigmented paint or adhesive and therefore provide little or no reflectance to a driver, poor and inaccurate bead distribution wherein not all of the beads are generally uniformly spread within the line and there is wastage of beads that miss the line and therefore do not get adhered thereto. Furthermore the retro-reflectivity may be biased according to the direction of application onto the road surface so that it is generally difficult to have beads that provide the same or similar reflectance both ways in terms of direction of travel of vehicles and especially for night time conditions. The excessive waste due to the beads not falling within the line marking is expensive and inefficient.
Wet weather places a further demand on the performance of road line marking. Typically minimal retro-reflectivity has been possible with wet road conditions due to the nature and placement of the beads. Road safety requirements are developing to a level where road line visibility will be a regulated requirement in wet night time conditions and as a consequence, the value of road line marking is linked to the level of retro-reflectivity that can be generated.
Road line marking is generally carried out at speed and as such, any objects being delivered from the vehicle will have a similar velocity such that when they contact the road surface they will roll or bounce unless the delivery system has the ability to control the placement.
The present invention seeks to overcome or ameliorate one or more of the disadvantages by providing a method and apparatus for applying reflective elements to a surface in such a way as to minimise rolling, bouncing and loss of control over the reflective element movement during application of the elements to the surface.
According to a first aspect of the invention there is provided dispensing apparatus for dispensing visual indication means onto a surface, said apparatus being attached to a vehicle and said visual indication means being applied to a previously marked region on said surface, said dispensing apparatus comprising:
inlet means for receiving said visual indication means;
outlet means for dispensing said visual indication means onto said surface;
drive means for driving said visual indication means along a path from said inlet means to said outlet means such that said visual indication means contact a surface of said drive means thereby imparting a predetermined velocity to said visual indication means;
wherein said visual indication means exit said outlet means at a velocity that has a magnitude substantially the same as the magnitude of velocity at which said vehicle travels and a direction that is substantially opposite to the direction of travel of said vehicle.
Preferably the visual indication means are reflective elements, such as glass beads. The drive means may include a rotor or drum having its rotational speed controlled in proportion to the velocity of travel of the vehicle. A feedback-type arrangement may be used to keep the exit velocity of the reflective elements substantially the same in magnitude but substantially opposite in direction to the velocity of the vehicle.
Said drive means may be housed in a drive housing and defining a gap between an interior surface of said housing and an exterior surface of said drive means. Said reflecting elements may be directed through said gap as part of the predefined path wherein said exterior surface of said drum contacts said reflective elements to enable said reflective elements to have the requisite velocity on exit from the outlet means.
According to a second aspect of the invention there is provided a method of applying visual indication means to a surface from a moving vehicle, wherein said visual indication means are dispensed from dispensing apparatus attached to said vehicle;
said method comprising the steps of:
loading said visual indication means to said dispensing apparatus;
imparting a predetermined velocity to said visual indication means through a drive means, said drive means driving said visual indication means along a path from inlet means of said dispensing apparatus to outlet means of said dispensing apparatus such that said visual indication means contact a surface of said drive means;
dispensing said visual indication means from said drive means onto a previously marked region of said surface;
such that the exit velocity of said visual indication means from said dispensing apparatus is substantially the same in magnitude as the velocity of travel of the vehicle but substantially opposite in direction to the direction of travel of the vehicle.
The method may further comprise the step of marking said region with a material capable of adhesion to said surface, such as a suitable adhesive material or paint prior to the application of said visual indication means, which may be reflective elements. The drive means may be controlled in accordance with the velocity of the vehicle through, for example a feedback arrangement, such that the angular speed of the drive means that imparts a velocity to the reflective elements is adjusted depending on the velocity of the vehicle.
The method may further comprise the step of comparing the angular speed or velocity of the drive means with the velocity of travel of the vehicle and controlling said angular speed in accordance with the velocity of travel of the vehicle.